Cathode ray tube manufacture



Dec. 9, 1969 e. L. FASSETT ET AL 3,482,286

CATHODE RAY TUBE MANUFACTURE Filed Jan. 7, 1966 5 Sheets-Sheet 2 Age/ii Dec. 9, 1969 5, ss ET AL 3,482,286

CATHODE RAY TUBE MANUFACTURE 5 Sheets-Sheet 5 Filed Jan. 7, 1966 fl) venion. 64:0? 1. films-n 6 MAR/41a; Kw AE/VSJEAI 1969 e. L. FASSETT ET AL CATHODE RAY TUBE MANUFACTURE Filed Jan. '7, 1966 5 Sheets-Sheet 4 N i m; n 6 A VM.K% M NW v E 5 w 2 MM x M0 w 1 7. 1 o v F I 1 3 1 M,

United States Patent 0 3,482,286 'CATHODE RAY TUBE MANUFACTURE Gardner L. Fassett and Marinus van Renssen, Lancaster, Pa., assignors to RCA Corporation, a corporation of Delaware Filed Jan. 7, 1966, Ser. No. 519,345 Int. Cl. H01 9/18; B23q 3/00 US. Cl. 29-25.13 18 Claims ABSTRACT OF THE DISCLOSURE face, means for fixedly supporting a rectangular shadow mask above the gauge member, means for moving the panel upwardly to bring the gauges in contact with the mask surface, means for adjusting the spacing between the panel and mask to produce a desired spacing at two gauges on a first diagonal of the mask, and means for rocking the panel about the other diagonal of the mask to produce equal spacing at two gauges on the other diagonal. The mask may be mounted on the panel in the final position, by welding to the mask four leaf springs which are detachably mounted on studs on the panel. Before mounting, the panel may be bodily moved, without rocking, toward or away from the mask a small distance, as measured by a central gauge, to optimize all of the spacings within a given acceptable tolerance. A similar manual method of adjusting the spacing and mounting the mask with respect to the faceplate panel is also disclosed.

The present invention relates to the manufacture of cathode ray tubes, and particularly to an improved method of assembling a multi-apertured shadow mask ia a predetermined spaced relation with an envelope faceplate panel or cap of a color picture tube or kinescope. As an example, the method will be described as applied to the assembly of a rectangular shadow mask adjacent to the phosphor mosaic screen of a rectangular tube panel.

The envelope of a color picture tube of the shadow mask type is made up of a funnel part having a neck portion in which a three-beam electron gun structure is mounted, and a panel part which is sealed to the large end of the funnel at a certain stage in manufacture of the tube. The panel comprises a transparent faceplate, on the inner surface of which a mosaic of three different color emitting phosphors is laid down, and having a side or peripheral wall on which the shadow mask is mounted. The faceplate has a curved inner surface, e.g., spherical, and the shadow mask has a similar, but not identical, surface positioned with a predetermined spacing Q, of the order of a half inch, from the faceplate, measured normal to the inner surface of the faceplate. In operation of the tube, electrons from each of the three beams pass through the apertures in the shadow mask and strike the phosphor dots of only one of the three colors. The phosphor dots for each color are usually formed on the faceplate by a photographic method using the shadow mask as a stencil. Thus, the shadow mask must be detachably mounted on the panel so that it can be easily removed and replaced in exactly the same position every time. The mask is usually mounted by means of at least three strap-like or leaf springs, each welded at one end to the mask or its frame 3,482,286 Patented Dec. 9, 1969 and having an aperture at the other end resiliently engaging an inwardly-extending fixed stud on the side wall of the panel. Heretofore, the Q spacing of the shadow mask from the faceplate has been determined by interposing a spacer member, having a plurality of studs of fixed predetermined length, between the faceplate and the mask, assembling the apertures of the leaf springs with the studs, and welding the springs to the mask with the spacer in contact with the mask and the faceplate. A disadvantage of this assembly method is that, since the mask is very thin, of the order of a few mils, it is practically impossible to assemble the mask with the spacer studs without distorting the mask, and this results in improper spacing of the mask from the faceplate after the spacer is removed and the parts re-assembled. An alternative is to shape one side of the spacer to fit the mask contour and use studs only on the faceplate side. However, due to variations in the contours of the masks, and faceplates, many masks which do not fit the spacer are scrapped even though the variations are such that they could have been used.

An object of the present invention is to provide an improved method of assembling a shadow mask with a faceplate panel of a cathode ray tube.

The foregoing and other objects are achieved in accordance with the present invention by: supporting a mask element and a panel element in given positions relative to each other; moving one of the elements relative to the other while measuring the spacing therebetween at several points to optimize the spacing with respect to a desired spacing. This may be done by measuring the spacing at two given points to produce a desired spacing at those points; and then, while maintaining the spacing at those points, rocking said one element about an axis joining said two points to another position at which the spacing between the two elements is substantially the same at two other points on opposite sides of said axis. The mask element may then be detachably mounted with respect to the panel element while the elements are held in this other position, as by welding spring straps to the mask. In the case of rectangular mask and panel elements, the two pairs of points are preferably located on the two diagonals of the rectangle.

In the example described herein, the mask element is held stationary and the panel element is moved toward and tilted relative to the mask element. However, the invention can be carried out by holding the panel stationary and moving the mask element toward and tilting it relative to the panel element. Instead of attaching the mask element to the panel element in the final position mentioned above, the spacing between the elements at the center thereof may be measured. Then, if necessary, the movable element may be moved bodily toward or away from the other element to average the three spacings, before attaching the mask element to the panel element.

The invention is described in greater detail in connection with the accompanying drawings, wherein;

FIG. 1 is a front elevation of a machine which may be used in carrying out the invention;

FIG. 2 is a vertical section of the machine of FIG. 1 taken on the line 2-2 of FIG. 3;

FIG. 3 is a top plan view of the machine;

FIG. 4 is a transverse section taken on line 4-4 of FIG. 1;

FIG. 5 is a transverse section taken on line 55 of FIG. 1;

FIG. 6 is a perspective view of a spacer-gauge assembly used with the machine of FIG. 1, and an indicating device which may be used therewith;

FIG. 7 is a longitudinal section of one of the gauges of FIG. 6; and

FIG. 8 is a fragmentary section view of a spring strap means for detachably mounting the mask on the panel in a color picture tube of the shadow mask type.

The major parts of the machine shown in the drawing are:

1. A fixed base;

2. A platform rotatably mounted on the base;

3. A first fixture on the platform for referencing and holding a shadow mask in a horizontal position with the screen side down;

4. A second fixture for referencing and holding a faceplate panel in a horizontal position beneath and vertically aligned with the mask, mounted on the platform for vertical and tilting movement;

5. A Q-spacing gauge member insertable between the panel and the mask;

6. Equipment for welding the leaf springs to the mask when the desired Q spacing has been achieved (not shown); and

7. Various machine controls (not shown).

Referring to the drawing, the machine comprises a horizontal base plate 1, supported on a structural iron framework 3. Three posts 5, attached to the top of the base plate 1, are provided with pairs of rollers 7 between which a circular platform or plate 9 is rotatably supported in a horizontal plane. An elongated tubular bearing member 11 extends vertically through a central aperture 13 in platform 9 to which it is fixed by a ring 15 welded to the member 11 and bolted to the plate 9. The lower end of bearing member 11 extends through a second bearing 17 mounted in an aperture 19 in the base plate 1.

An elongated cylindrical panel support rod 21 extends through the bearing member 11 for vertical sliding movement therein. An apertured circular plate 23 is suspended from the upper end of rod 21 by a ring member 25 and tubular member 27, as shown in FIG. 2. A rectangular panel supporting plate 29 is supported from plate 23 for tilting and incremental vertical movement by three air servo motor units 31, identified as 31A, 31B and 31C.

Each of the three units 31 comprises a fixed support 33 mounted on the plate 23, an air chamber 35 suspended by two rods 36 from support 33 and including a flexible diaphragm 37 connected at its center to a spring-loaded rod 39 extending vertically through a locking cylinder 41 on the support 33. Each rod 39 is connected to one of three blocks 42A, 42B and 42C attached to plate 29 by a ball 43 on rod 39 and a transverse cylindrical groove 44 in each block. The grooves 44 in blocks 42A and 420 are aligned with each other and the grooves 44 in block 42B is oriented at 90 to the axis 46 of the other two grooves. The block 42A has a thickness equal to the diameter of its ball 43 and its groove 44 is closed by two plates to form a ball-and-socket joint. The locking cylinder 41 contains a thin flexible sleeve closely surrounding the rod 39 and a fluid chamber for pressing the sleeve against the rod 39, to lock the latter in a desired position (not shown).

The plate 29 is provided with three non-metallic panel supporting pads 48, shaped to fit the external panel contour. Also mounted on the plate 29 are three fixed brackets 49 at two corners and a spring-loaded movable bracket 51 at a third corner, for positioning the tube panel P on the pads 48 coaxial with the axis of rotation of the platform 9.

The shadow mask S is supported in fixed position above the panel support plate 29 by means including three vertical posts 53, 55 and 57 mounted on the rotary platform 9, in the positions shown in FIG. 4. Semi-circular notches 58 in the periphery of the plate 23 provide clearance for the posts 53, 55 and 57. A horseshoe-shaped horizontal support member 59 is mounted on the top of the posts 53, 55 and 57. The rectangular mask S supported at the four corners by four electromagnets 61 carried by four L-shaped support members 63 mounted on the member 59. Three of the electromagnets have fixed iron armatures 65 surrounded by energizing coils 67 and carried by blocks '69 on the members 63. The fourth electromagnet 61, located at the upper left corner in FIG. 3, comprises a movable elongated iron armature 71 which extends through an energizing core in the member 63, like the fixed armatures 65, and also through a nonmagnetic block 73 having a vertical armature bore and two horizontal armature bores which intersect the vertical bore, as shown in the cut-away portion of FIG. 3. Two auxiliary iron armatures 75 are disposed in the horizontal bores for locking the vertical armature 71 in a desired position when energized by coils 77. In order to minimize distortion of the mask frame 81 due to the Weight of movable armature 71, the armature is springloaded to support most of its Weight. The mask S is mounted by engaging three corners of the radial flange 79 of its rigid frame 81 (FIGS. 3 and 8) with the lower ends of the three fixed armatures 65 and energizing the coils 67. Then, the coils 77 are energized to cause the armatures 75 to lock the armature 71 in place, and then the coil 67 of armature 71 is energized to clamp that armature to the mask frame 81. In order to laterally position the mask S in a predetermined position, six vertically extending locating pins 83 are attached to the support members 63, by means of blocks 85, in the locations shown in FIG. 3.

As shown in FIG. 2, the upper end of the bearing member 11 serves as a stop and support for the ring member 25 and associated panel support structure when the panel support is in its lowest position. The panel support is raised, to assemble the panel P with the mask S, by means of an air motor 87 which is mounted on the base plate 1 and connected to the lower end of the panel support rod 21 by a lever 89 pivoted to the framework 3 at 91. The lever 89 is connected to the rod 21 by a double pin-and-annular groove type of connection 91 to permit rotation of the rod 21. The upward movement of the rod 21 is limited by an adjustable stop 93 which engages the lever 89. A plate 94, attached to the plate 23 and having a circular opening 95 fitting the post 57, serves as a vertical guide to prevent rotation of plate 23 while permitting vertical movement thereof with respect to the platform 9.

A motor 96, mounted on the framework 3, is connected by means including gears 97 and 99 to the ring 15, for rotating the platform 9 to different positions during the operation of the machine under control of a cam-operated switch 101.

FIGS. 2 and 6 show a Q-space gauge member 103 that is positioned on the faceplate surface 105 of the panel P before the panel is assembled with the mask S. The gauge member 103 comprises a relatively thin rectangular sheet 107, e.g. an eighth inch sheet of Fiberglas or plastic, having a surface contour conforming substantially to the contour of the faceplate surface 105. Four air-operated distance gauges 109, identified as 109A, 109B, 109C and 109D, are flexibly mounted on the sheet 107 at the four corners of a rectangle. Preferably, a fifth air gauge 109E is mounted at the center of the sheet 107. As shown in FIGS. 2 and 6, the four gauges 109 are located at four points substantially equidistant from the projection of the central gauge 10913. As shown in FIG. 7, each of the air gauges 109 comprises an elongated block 111 having a fixed projection 113 on one side and a movable projection 115 on the opposite side. The movable propection 115 is carried at one end of an elongated leaf member 117 pivoted at 119 on the block 111 at a point nearer to but spaced from the other end of the member. The portion 121 of the member 117 extending beyond the pivot normally lies close to a small air port 123 in the block 111 which communicates by a hose 125 with a regulated source of air pressure (not shown). In operation, downward movement of the projection 115 is accurately measured by the change in back pressure at the source resulting from the upward movement of portion 121 away from the port 123. The different back pressures from the five gauges may be displayed by different columns 127 of liquid in the meter 129, as shown in FIG. 6. The scales on the meter may be calibrated in mils, for example, of measured movement of the movable projections 115.

FIG. 8 shows a means for detachably mounting the shadow mask frame 81 on the panel P by means of a leaf spring 131 fixed at one end to the frame 81 and having a hole 133 at the other end detachably engaging a stud on the panel. Instead of welding the'spring 131 directly to the frame 81, a hook plate 135 is first welded to the frame. Then, the spring 131 is inserted into the hook portion of the plate 135 and engaged with the stud 137, whereby the Spring is resiliently held in place during the final adjustment of the mask with respect to the panel after which the spring .131 is welded to the hook plate 135. Preferably, four such masks mounting means are used, one at or near the middle of each of the long and short sides of the mask.

The machine described above is used to perform the method of the present invention in the following manner. The panel P and mask S are mounted on their respective pads 48 and electromagnets 61, as described above. The Q-space gauge member 103 is placed in the panel P and substantially centered therein with the fixed projections 113 resting on the face plate surface 105, as shown in FIG. 2. Then, the air motor 87 is actuated to raise the rod 21, plate 23, plate 29 and panel P to the upper position in which the panel P surrounds the mask S, as shown in phantom lines in FIG. 2. The stop 93 is adjusted to stop the upward movement of the panel P just before the gauge projections 115 engage the mask surface. Then, the two air servo motor units 31A and 310 on one diagonal of the panel support are energized to incrementally raise and tilt the panel support plate 29 until the two corresponding gauges 109A and 109C on the same diagonal of the panel measure the desired Q-spacing, as indicated by the meter 129.

The other air motor unit 311B is now energized to tilt the plate 29 about the first diagonal until the gauges 109B and 109D measure equal Q-spacing at two points on the other diagonal of the panel. If the measured Q-spacing 0n the second diagonal is within the allowable tolerance from the desired spacing, all of the units 31 could be locked by the locking cylinders 41, followed by assembly and welding of the mask mounting springs 131 to the mask S. After welding of the springs to the frame, the mask S is released from the magnets 61 by de-energizing the four coils 67, the panel support plate 29 is lowered, and the mask is detached from the panel to permit removal of the gauge 103, and other operations.

In some cases, even though the measured Q-spacings on the two diagonals of a particular mask-panel pair are satisfactory, the Q-spacing at the center is not within the allowable tolerance. Thus, after the second tilting operation described above, and prior to the welding of the springs 131, the Q-spacing at the center is preferably also measured by gauge 109E. Then, if necessary, all three of the air motor units are re-adjusted to optimize the two diagonal spacings with the center spacing, to bring all of the Q-spacings within the allowable tolerance, wherever possible. In practice, it has been found that very few mask-panel pairs cannot be successfully assembled by this method.

The mask mounting springs 131 may be assembled with the panel studs 137 and the hooks 135a of the hookplates 135 before or after the Q-spacing adjustment procedure described above. After the Q-spacing adjustment has been completed, the springs 131 are welded permanently to the hookplates 135. With a portable or hand-carried welder all of the springs could be welded without rotating the platform 9 and the mask-panel pair carried thereby. However, the machine parts are designed for rotation as described above in order to permit indexing each of the mask-mounting points to a single welding station (not shown). Moreover, rotation of the mask-panel assembly facilitates hand welding.

It has been noted that the operation of welding the springs 131 to the mask hokplates 135 heats up the mask, and the expansion thereof causes the Q-spacing after welding to be a few mils less than the desired value. To compensate for this, after the measured Q-spacings at the various gauge points have been optimized as described above, the mask S is moved bodily away from the panel P a predetermined amount, prior to the welding of the springs 131 to the mask. The amount of such movement depends upon the manner of welding and the size of the cathode ray tube being manufactured. In the case of a mask and panel for a 19" rectangular tube with deflection and heliarc welding, this amount is about 6 mils.

As an example, the method of the invention has been described in connection with a particular machine which, under control of the operator, performs most of steps of the method. However, the method has been performed successfully by performing most of the steps by hand. In this case, the panel is held in a position like that shown in FIG. 1 by a plurality of pads on a fixed base; a Q-spacing gauge member, similar to the gauge member 103, is placed on the faceplate surface; a mask is inserted within the panel over the gauge member and temporarily mounted on the panel studs by means of leaf springs frictionally engaging hook plates, as shown in FIG. 8; the mask is grasped at two points on a first line and moved up and down and rocked until the desired Q spacing is produced on the first line, as measured by the gauges and associated meter; the mask is grasped at two points on another line and tilted to equalize the Q-spacing on the other line; and then the mask springs are welded to the mask frame and the insert gauge is removed. Thus, the only items of equipment necessary are the panel support base, Q-spacing gauge member and meter, and welder.

On the other hand, the machine described may include means for automatically actuating the air motors 31, in response to the measurements recorded by the gauges 109, to position the mask S in the desired final position with respect to the panel P, ready for welding of the spring 131 to the mask frame 81.

What is claimed is:

1. In the manufacture of a cathode ray tube comprising a curved faceplate and a multi-apertured shadow mask having a surface contour similar to that of said faceplate spaced from said faceplate; the method of mounting said mask with respect to said faceplate c0mprising the steps of:

(a) supporting said faceplate in a given position;

(b) placing on said faceplate a gauge member having four or more spaced variable distance-measuring gauges with one end of each gauge contacting said faceplate;

(c) placing said mask in contact with the other ends of said gauges;

(d) adjusting the distances between said mask and said faceplate, as measured by said gauges, to optimize said distances with respect to a desired distance; and

(e) then detachably mounting said mask with respect to said faceplate with said distances optimized.

2. The method of claim 1, comprising the subsequent steps of:

(a) removing said mask and gauge member; and

(b) then mounting said mask on said faceplate.

3. The method of claim 1, wherein said mask is mounted on said faceplate in the last step.

4. The method of claim 3, wherein said faceplate has a peripheral wall portion to which a plurality of mask mounting studs are fixed, and said mounting step comprises the fixing to the periphery of said mask of a corresponding plurality of leaf springs having openings engaging said studs.

5. In the manufacture of a cathode ray tube comprising a curved faceplate element, a multi-apertured mask element having a surface contour similar to that of said faceplate element spaced from said faceplate element; the method of mounting said mask element with respect to said faceplate element comprising the steps of:

(a) supporting said mask element in a given position;

(b) supporting said faceplate element in a position spaced from said mask element;

(c) adjusting the position of one of said elements, while measuring the spacing between said elements at two given points substantially equidistant from the center of said faceplate, to produce a desired spacing at said two points; and

(d) then, while maintaining said spacing at said two points, further adjusting said one element by rocking it about an axis joining said two points to another position at which the spacing measured between said elements is substantially equal at two other points substantially equidistant from the center of said faceplate and on opposite sides of said axis. 6. The method of claim 5, comprising the subsequent step of moving said one element bodily towards or away from the other element while maintaining equal spacings at each pair of said points, to another position at which said spacings are optimized with respect to said desired spacing.

7. The method of claim 5, comprising the subsequent steps of:

(a) measuring the spacing between said elements at the center thereof; and

(b) then moving said one element bodily towards or away from the other element while maintaining equal spacings at each pair of said points, to another position at which all of said spacings are optimized with respect to said desired spacing.

8. The method of claim 5, comprising the subsequent step of detacha bly mounting said mask element with respect to said faceplate element with said one element in said other position.

9. The method of claim 8, wherein said faceplate has a peripheral wall portion to which a plurality of mask mounting studs are fixed, and said mounting step comprises the fixing to the periphery of said mask of a corresponding plurality of leaf springs having openings engaging said studs.

10. The method of claim 9, wherein said mask and faceplate are generally rectangular in shape, and said mask is located within and detachably mounted on said peripheral wall portion by four of said leaf springs welded to said mask and engaging four studs located substantially at the midpoints of the four sides of the rectangular faceplate.

11. The method of claim 5, wherein said mask element is held in a fixed position, and said faceplate element is initially positioned below said mask element with its screen side up and then moved upward towards said mask element to said other position.

12. The method of claim 5, comprising the subsequent step of moving said one element bodily relative to the other element a predetermined amount, to compensate for changes in spacing during the subsequent mounting operation, and then fixing devices to said mask for detachably mounting said mask with respect to said faceplate.

13. The method of claim 5, wherein said faceplate and mask elements are generally rectangular in shape, and said spacing is measured at four points located substantially on the two diagonals of the faceplate element.

14. A cathode ray tube comprising a curved faceplate, and a multi-apertured mask having a surface contour similar to that of said faceplate mounted in spaced relation to said faceplate; said mask and faceplate being spaced from each'other at two points on a circle of given radius substantially concentric with said faceplate by a predetermined desired distance, and being spaced from each other at two other points on said circle and on opposite sides of -a straight line joining said first-named two points by equal distances which differ from said predetermined distance by an amount greater than zero 'but not greater than a predetermined acceptable tolerance.

15. A cathode ray tube as in claim 14, wherein the two points of each pair of points are diametrically opposite each other on said circle.

16. A cathode ray tube as in claim 15, wherein said faceplate and mask are generally rectangular in shape, and said four points are located substantially on the two diagonals of said faceplate.

17. The method of assembling a cathode ray tube comprising a curved faceplate and a multi-apertured shadow mask having a surface contour similar to that of said faceplate spaced from said faceplate, comprising the steps of spacing said mask from said faceplate such that measured spacings therebetween at two points on a circle of given radius are equal to a given desired distance and measured spacings therebetween at two other points on said circle differ from said given distance by small tolerable values greater than zero, and maintaining said spacings by mounting said mask with respect to said faceplate.

18. In the manufacture of a cathode ray tube comprising a curved faceplate and a multi-apertured mask having a surface contour similar to that of said faceplate mounted in spaced relation to said faceplate; the method of mounting said mask with respect to said faceplate comprising the steps of:

(a) supporting said mask and faceplate in relativelymovable spaced relation;

( b) measuring the distances between said mask and faceplate at four points on a circle of given radius substantially concentric with said faceplate;

(c) adjusting the spacing between said mask and faceplate so that (I) said distances measured at two of said points are equal to a predetermined desired distance, and

(2) said distances measured at two other of said points on opposite sides of a straight line joining said first-named two points are equal and differ from said desired distance by an amount greater than zero but not greater than a predetermined acceptable tolerance; and

(d) then mounting said mask with respect to said faceplate with said adjusted spacing therebetween at said four points.

References Cited UNITED STATES PATENTS 2,879,601 3/1959 Canfield 33-174 XR 3,187,404 6/1965 Fiore 2925.l XR 3,335,479 8/1967 Morrell 292S.l3 XR FOREIGN PATENTS 633,645 12/1961 Canada.

JOHN F. CAMPBELL, Primary Examiner RICHARD B. LAZARUS, Assistant Examiner US. Cl. X.R.

2925.ll, 464, 468; 313-64, 92; 3l623, 29 

